1. Field of the Invention
The present invention relates to a color image color shift correction method and color image imaging apparatus and, more particularly, to a new technique for determining a color shift caused by a shift between color images of color planes such as RGB ones.
2. Description of the Related Art
Generally, a field sequential color image imaging apparatus rotates a rotary color filter with RGB color filters. Simultaneously with this, the apparatus images an object by a monochrome imaging apparatus through each color filter every time the color filter moves onto the optical axis of a photographing optical system and sequentially takes in images of respective colors. Then, the apparatus combines the images to obtain a color image.
A field sequential color image imaging apparatus of this type cannot ensure sufficient orthogonal accuracy of the plane of each color filter with respect to the photographing optical axis due to a swing of the rotation axis of the rotary color filter and the accuracy in attaching the color filter. For this reason, the position of an object image is shifted on the imaging surface according to the rotational position of the rotary color filter.
To solve this problem, a field sequential color camera described in Japanese Patent Application Laid Open No. 6-319143 finely displaces a two-dimensional solid state imaging element in response to displacement of an optical image caused by the rotation of a rotary color filter. More specifically, the invention described in Japanese Patent Application Laid Open No. 6-319143 focuses attention on that when the rotary color filter is tilted with respect to the photographing optical axis, the locus of a certain point of the optical image forms a circle on the imaging surface along with the rotation of the rotary color filter. According to the invention, the two-dimensional solid state imaging element is made to move in a circle in sync with the rotation of the rotary color filter.
Since sequential imaging is performed while switching between color filters, there is a shift, between the color filters, in the position of an object image on the imaging plane when the object is moving. Japanese Patent Application Laid Open No. 6-217328discloses a technique for correcting a color shift by detecting a motion vector quantity between field sequential images and performing pixel shift for the images according to the motion vector quantity. In detecting the motion vector quantity between images, correlation calculation between the images is performed, and a vector quantity in which the correlation is the maximum is detected.